High-Resolution Magic-Angle Spinning-1H-NMR Spectroscopy-Based Metabolic Profiling of Hippocampal Tissue in Rats with Depression-Like Symptoms.

Depressive disorders cause large socioeconomic effects influencing not only the patients themselves but also their family and broader community as well. To better understand the physiologic factors underlying depression, in this study, we performed metabolomics analysis, an omics technique that comprehensively analyzes small molecule metabolites in biological samples. Specifically, we utilized high-resolution magic-angle spinning-1H-NMR (HRMAS-1H-NMR) spectroscopy to comprehensively analyze the changes in metabolites in the hippocampal tissue of rats exposed to chronic stress (CS) via multi-step principal component analysis (multi-step PCA). The rats subjected to CS exhibited obvious depression-like behaviors. High correlations were observed between the first principal component (PC1) score in the score plot obtained using multi-step PCA and measurements from depression-like behavioral testing (body weight, sucrose preference test, and open field test). Alanine, glutamate, glutamine, and aspartate levels in the hippocampal tissue were significantly lower, whereas N-acetylaspartate, myo-inositol, and creatine were significantly higher in the CS group compared to the control (non-CS) group. As alanine, glutamate, and glutamine are known to be involved in energy metabolism, especially in the tricarboxylic acid cycle, chronic exogenous stress may have induced abnormalities in energy metabolism in the brains of the rats. The results suggest that N-acetylaspartate and creatine levels may have increased in order to complement the loss of energy-producing activity resulting from the development of the depression-like disorder. Multi-step PCA therefore allowed an exploration of the degree of depression-like symptoms as represented by changes in intrinsic metabolites.

Short-term feeding at the wrong time is sufficient to desynchronize peripheral clocks and induce obesity with hyperphagia, physical inactivity and metabolic disorders in mice.

BACKGROUND: The circadian clock regulates various physiological and behavioral rhythms such as feeding and locomotor activity. Feeding at unusual times of the day (inactive phase) is thought to be associated with obesity and metabolic disorders in experimental animals and in humans. OBJECTIVE: The present study aimed to determine the underlying mechanisms through which time-of-day-dependent feeding influences metabolic homeostasis. METHODS: We compared food consumption, wheel-running activity, core body temperature, hormonal and metabolic variables in blood, lipid accumulation in the liver, circadian expression of clock and metabolic genes in peripheral tissues, and body weight gain between mice fed only during the sleep phase (DF, daytime feeding) and those fed only during the active phase (NF, nighttime feeding). All mice were fed with the same high-fat high-sucrose diet throughout the experiment. To the best of our knowledge, this is the first study to examine the metabolic effects of time-imposed restricted feeding (RF) in mice with free access to a running wheel. RESULTS: After one week of RF, DF mice gained more weight and developed hyperphagia, higher feed efficiency and more adiposity than NF mice. The daily amount of running on the wheel was rapidly and obviously reduced by DF, which might have been the result of time-of-day-dependent hypothermia. The amount of daily food consumption and hypothalamic mRNA expression of orexigenic neuropeptide Y and agouti-related protein were significantly higher in DF, than in NF mice, although levels of plasma leptin that fluctuate in an RF-dependent circadian manner, were significantly higher in DF mice. These findings suggested that the DF induced leptin resistance. The circadian phases of plasma insulin and ghrelin were synchronized to RF, although the corticosterone phase was unaffected. Peak levels of plasma insulin were remarkably higher in DF mice, although HOMA-IR was identical between the two groups. Significantly more free fatty acids, triglycerides and cholesterol accumulated in the livers of DF, than NF mice, which resulted from the increased expression of lipogenic genes such as Scd1, Acaca, and Fasn. Temporal expression of circadian clock genes became synchronized to RF in the liver but not in skeletal muscle, suggesting that uncoupling metabolic rhythms between the liver and skeletal muscle also contribute to DF-induced adiposity. CONCLUSION: Feeding at an unusual time of day (inactive phase) desynchronizes peripheral clocks and causes obesity and metabolic disorders by inducing leptin resistance, hyperphagia, physical inactivity, hepatic fat accumulation and adiposity.